1. Field of the Invention
The present invention relates generally to a lens unit of a TV camera, and more particularly to a lens unit that automatically moves a movable lens to a security position when the lens unit becomes unused.
2. Description of Related Art
A detachable lens unit of a TV camera is normally disconnected from the camera after the camera is used if it is used outdoors, and the detached lens unit is housed in a container during the transportation. If the TV camera is attached to a pedestal as is the case with a TV camera that is used at a studio, the lens unit may be kept in the attached state during the transportation of the camera to a warehouse for example.
The lens unit is sometimes vibrated strongly and shocked while it is transported in the state of being housed in the container, or in the state of being attached to the camera with the pedestal. In this case, gears and cam grooves, which drive movable lenses with a motor, may become loose, deteriorating the operability and optical performance of the lens unit. Moreover, the lens unit may be broken sometimes.
The present invention has been developed under the above-described circumstances, and has as its object the provision of a lens unit of a TV camera, which prevents the deterioration of the operability and optical performance of the lens unit due to the vibrations and shocks during the transportation.
To achieve the above-mentioned object, the present invention is directed to a lens unit of a TV camera, the lens unit being attached to a camera body of the TV camera, the lens unit comprising: at least one movable lens, the movable lens being movable in a moving range during shooting; a moving means for moving the movable lens; an ascertaining means for ascertaining whether the lens unit is used or unused; and a control means for driving the moving means to move the movable lens to a predetermined position when the ascertaining means detects that the lens unit becomes unused.
According to the present invention, when it is detected that the lens unit becomes unused, the movable lens is moved to the predetermined position. To ascertain whether the lens unit is used or unused, the ascertaining means may ascertain whether a power supply of the camera body is in operation or not, or the ascertaining means may ascertain whether the lens unit is attached to the camera body or not.
The predetermined position may be within the moving range of the movable lens. The lens unit may permit looseness of positional accuracy of the movable lens at the predetermined position during shooting. The moving means may be reinforced for the predetermined position of the movable lens. If the movable lens is a focus lens, the predetermined position may be an infinity end of the moving range of the focus lens. If the movable lens is a zoom lens, the predetermined position may be a wide angle end of the moving range of the zoom lens.
The predetermined position may be outside the moving range of the movable lens. If the movable lens is the focus lens, the predetermined position may be beside the infinity end of the moving range of the focus lens. If the movable lens is the zoom lens, the predetermined position may be beside the wide angle end of the moving range of the zoom lens.
A stopper may be provided for limiting the movable range during shooting. The limitation of the stopper is released to enable the movable lens to move to the predetermined position when the ascertaining means detects that the lens unit becomes unused.
The control means may drive the moving means to move the movable lens from the predetermined position to an initial position when the ascertaining means detects that the lens unit becomes used. The initial position may be a position of the movable lens when the ascertaining means detects that the lens unit becomes unused.
An auxiliary power supply may be provided for supplying power to the lens unit when the ascertaining means detects that the lens unit becomes unused. The auxiliary power supply may be turned off when the movable lens reaches the predetermined position, or when a predetermined period of time has passed since the lens unit becomes unused. The auxiliary power supply may be one of a condenser and a secondary battery that are charged by the power supply of the camera body, or a primary battery.